In recent years, new technologies have allowed us to better characterize the heterogeneity of breast cancer and to identify a number of biological subtypes based on their molecular profiles. Consequently, molecular classification of tumors is increasingly being used to guide treatment selection and new treatment development, in evaluating prognosis, and in studies of etiology. One molecular classification, the intrinsic subtype, which distinguishes among breast cancers based on either their cell type of origin (luminal A/B or basal) or whether the tumor is HER2-positive, has been used to identify biologically and clinically distinct subtypes of breast cancer. The primary goal of this proposal is to examine the effects of intrinsic subtypes and their relationship to breast cancer risk factors and short and long-term prognosis in two ongoing cohort studies of breast cancer survivors (N=4177) being conducted within the Kaiser Permanente of Northern California (KPNC) Medical Care program. The first study, the Life After Cancer Epidemiology (LACE) cohort, a population-based cohort of 2,288 women diagnosed with Stage I>1 cm, II, or IIIa breast cancer, was established in 2000- 2002 to examine behavioral factors and breast cancer prognosis. These data will be combined with 1890 additional cases of similar stage from the Pathways cohort, a study of short term breast cancer survivors which began in January 2006. Given the inconsistency observed to date in findings between energy related factors and prognosis and the suggestion that effects may vary by tumor characteristics such as hormone receptor status, a secondary goal of this proposal is to examine whether specific behaviors related to energy balance may be related to prognosis among breast cancer patients in general or primarily among women with certain intrinsic subtypes Since most studies have only reported on effects of energy related factors on short term prognosis, another secondary goal of this proposal is to continue to follow women in the LACE cohort up until 15 year post-diagnosis and to examine the relationship of energy related lifestyle factors with long-term prognosis. Data on weight, weight change, physical activity and diet were collected at multiple time points post diagnosis. Women are followed annually for recurrence and death by self report and verified by medical record and death certificates. During the proposed new funding period, archived tumor blocks will be retrieved and, using immunohistochemical assays (IHC), breast cancers will be classified into intrinsic subtypes. This study will achieve tremendous cost savings by examining the proposed questions within two existing cohort of cancer survivors for whom post diagnosis data on behavior are already available and by retrieving tumor specimens within a cohort where close to 90% the women belong to the KPNC, an HMO, where tumor specimens are readily accessible. Our proposal addresses a range of issues that are emerging priority areas in cancer survivorship research which will have both clinical and public health impact.